1. Field of the Invention
The invention relates generally to improved methods and systems for offshore mooring of vessels. In particular aspects, the invention relates to improved methods of configuring a berth and systems for docking maritime vessels at an offshore location. The berth may be used for the following purposes: loading or unloading of cargo; unloading of passengers; refueling or maintenance and repair of maritime vessels. Maritime vessels, in the context used, include naval or commercial ships, barges, tugs, offshore floating platforms and specialty vessels used for the offshore industries.
2. Description of the Related Art
An effective berth requires that the floating dock be able to sustain large forces from docking vessel impacts, winds, waves, and currents against the maritime vessel while it is at berth. The berthing arrangement must also permit the safe transfer of cargo, passenger crew, and components for maintenance or provisions from the maritime vessel to the floating dock. Additionally, a tanker captain or harbor pilot must be comfortable or somewhat familiar with the berthing facility in order to safely maneuver the ship and prevent novel and unfamiliar docking procedures to be used. The berthing facility should be economical, thereby allowing its construction and installation without undue expense that might otherwise eliminate or limit its practical use.
Although floating docks are commonly used for docking of pleasure craft in yacht marinas, such an arrangement would not be suitable for use in deep water or for use with the offloading and loading of dangerous cargos in deeper areas farther from shore and from the general populace. The offshore application of a floating berth must account for required durability and safety.
Known berthing arrangements for maritime vessels at sea are not optimal and include inherent risks during transfer of hazardous cargo. U.S. Pat. No. 6,546,739 issued to Frimm et al., for example, teaches a floating platform, such as a modified very large crude carrier (VLCC) that is tethered to a turret system or a CALM buoy, that is moored in place. The tether connection is a single-point mooring that allows for “weathervaning,” or movement of the tanker about that mooring point during current, waves or wind changes. Such movement of the tanker during offloading or during sensitive cargo transfer to another vessel is problematic because the relationship between the tankers can change quickly and such an arrangement may become substantially unstable in poor weather or sea conditions.